Pulmonary Embolism, Thrombosis and Infarction

Pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)

Segmental pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)

• Lungs are strategically situated to catch emboli carried in venous blood
• Because the lung is supplied by both pulmonary and bronchial arteries and has extensive collateral channels, infarction usually does not follow embolism or thrombosis unless pulmonary circulation is already compromised
• In animals, greatest risk comes from:
  • Tumor emboli
    • From e.g.: osteosarcoma and haemangiosarcoma in dogs, uterine carcinoma in cattle
  • Septic emboli
    • From bacterial endocarditis, jugular thrombophlebitis, hepatic abscesses etc.
    • May cause unexpected death if in large numbers
    • May develop suppurative pneumonia -> pulmonary abscesses, arteritis, thrombosis
• Pulmonary infarcts usually occur when there is embolisation or thrombosis during general circulatory collapse or passive congestion of heart failure
• Pulmonary thromboembolism is a sequel to in cattle to large emboli from liver abscesses close to the vena cava
  • Death may ocur due to massive haemorrhaging into lung tissue
• Parasites (e.g. Dirofilaria immitis, Angiostrongylus vasorum) may be responsible
• Long-term intravenous catheterisation may cuse thrombi pieces breaking off and lodging in pulmonary vessels